General Philosophy

1
General Philosophy
Dr Peter Millican, Hertford College
Lecture 3Induction
2
Humes Fork

• Enquiry IV starts with a vital distinction
  between types of proposition
• Relations of ideas can be known a priori (i.e.
  without dependence on experience) by inspecting
  ideas hence their falsehood is inconceivable and
  they are necessarily true.
• e.g. Pythagoras Theorem. (E 4.1)
• 3 5 ½ 30. (E 4.1)
• All bachelors are unmarried.
• The modern term is analytic (as understood e.g.
  by Ayer) true in virtue of its meaning.

3
Matters of Fact

• Matters of fact cant be known a priori, and
  their truth / falsity are equally conceivable
• e.g. The sun will rise tomorrow. (E 4.2)
• The sun will not rise tomorrow. (E 4.2)
• This pen will fall when released in air.
• The modern term is synthetic a proposition whose
  truth is determined by the facts of experience
  (Ayer, LTL 1971, p. 105).
• So how can I discover a matter of fact which I
  neither perceive directly, nor remember?

4

• Suppose we see a yellow billiard ball moving
  towards a red one and colliding with it. We
  expect the red one to move but why?
• Because we suppose a causal connexion between the
  two events. But in that case
• How do we learn about causes and effects?

5
A Thought Experiment

• Imagine Adam, newly created by God, trying to
  envisage the effect of the collision

• how could he possibly make any prediction at
  all in advance of experience?

6
The Need for Extrapolation

• All inference to matters of fact beyond what we
  perceive or remember seems to be based on
  causation, and all our knowledge of causal
  relations comes from experience.
• Such learning from experience takes for granted
  that observed phenomena provide a guide to
  unobserved phenomena.
• We thus extrapolate from past to future on the
  assumption that they resemble. But do we have a
  rational basis for doing so?

7
Four Kinds of Evidence

• It is common for Philosophers to distinguish the
  Kinds of Evidence into intuitive, demonstrative,
  sensible, and moral. (Letter from a Gentleman,
  1745, p. 22)
• By intuition, Hume means immediate
  self-evidence the way we know that something is
  identical with itself, or that 2 is greater than
  1.
• Sensible evidence means from the senses.
• Demonstrative and moral reasoning are now
  commonly called deduction and induction

8
Locke on Reasoning

• In demonstrative reasoning, each link in the
  inferential chain is intuitively certain.
• reasoning concerning relations of ideas Hume
• In probable reasoning, some links in the
  inferential chain are merely probable.
• moral reasoning, reasoning concerning matter
  of fact Hume factual inference for short
• For Locke, both types of reasoning involve
  rational perception of the links (IV xvii 2).

9
Hume on Inferring Uniformity

• What ground can we give for extrapolating from
  observed to unobserved?
• Self-evident intuition? No.
• Demonstrative reasoning? No neither of these,
  because its clear that extrapolation could fail,
  so it cant be a matter of pure logic.
• Sensory knowledge? No what we perceive of
  objects gives us no insight into the basis of
  their powers, hence no reason to extrapolate.
• Factual inference? No that would be circular.

10
Review The Part (i) Argument

• All factual moral, probable inference is
  founded on causation
• Because causation is the only relation that
  enables us to infer from one thing to another.
• All knowledge of causal relations is founded on
  experience
• A priori, we can know nothing of causation.
• Hence all factual inference is founded on
  experience.

11
The Pivot

• All factual inference is founded on experience.
• All inference from experience is founded on a
  principle of uniformity or similarity.
• Because it requires that we extrapolate from our
  experience, on the basis that what we have not
  yet experienced will be similar.
• Hence all factual inference is founded on this
  Uniformity Principle.

12
The Part (ii) Argument

• But neither intuition, nor sensation, nor
  demonstration can ground such a principle.
• And factual inference as we have seen itself
  depends on the Uniformity Principle, so any
  attempt to establish the Principle by factual
  inference will be arguing in a circle.
• It follows that there is no rational basis for
  the supposition of Uniformity, and hence no
  rational basis for factual inference.

13
The Basis of Factual Reason

• Our Reason is fundamentally based on a brute
  assumption of uniformity, rather than any insight
  into the nature of things.
• Hence human reason differs from animal reason
  only in degree.
• Lockes supposed perception of probable
  connexions is wishful thinking.
• No causal interactions are really intelligible
  we discover what causes what not by pure thought,
  but by observation of uniformities.

14
Does This Imply Irrationalism?

• Does Hume deny that inductive inference is
  founded on any sort of rational insight into why
  nature should be uniform?
• YES!
• Does Hume think that all inferences about matter
  of fact are equally hopeless, so that theres no
  rational ground for preferring one to another?
• NO!

15
The Problem of Demarcation

• Religious belief is founded on whimsies and
  prejudices of the imagination.
• Science is founded on the instinctive,
  non-rational belief in uniformity.
• So what right has Hume to prefer science over
  superstition? His answer is to favour
  reasoning consistently with this irresistible
  instinctive belief, which is so utterly essential
  to human life and thought.

16
Implications for Science

• Systematisation rather than Intelligibility
• the utmost effort of human reason is, to reduce
  the principles, productive of natural phenomena,
  to a greater simplicity, and to resolve the many
  particular effects into a few general causes
  But as to the causes of these general causes, we
  in vain attempt their discovery. (E 4.12)
• Instrumentalism
• Newtons instrumentalist attitude to gravitation
  thus provides a model of good science.

17
The Gap in Humes Argument

• Hume takes for granted that all probable
  arguments must be based on experience.
• So it might be possible to escape his argument if
  induction could be justified using a priori
  probabilistic considerations.
• Though most philosophers are sceptical,
  interesting attempts have been made by
• Bruno De Finetti (1937), D.C. Williams (1947),
  David Stove (1986), Sir Roy Harrod (1956), Simon
  Blackburn (1973), J. L. Mackie (1979)

18
Other Attempts to Answer Hume

• Analytic Justification of Induction
• Induction is rational by definition it is partly
  constitutive of our concept of rationality.
• Inductive Justification of Induction
• Induction is justified by its past success.
• Pragmatic Justification of Induction
• We are pragmatically (rather than epistemic-ally)
  justified in relying on induction, because it
  will work if any method of prediction will.

19
Hume versus Strawson

• P. F. Strawson (Univ and Magdalen) fam-ously
  advocated the Analytic Justification.
• However its not clear that it really engages
  with Humes problem. Hume himself would agree
  that we call induction rational, and even that
  were right (in a sense) to do so.
• His sceptical result doesnt concern this use of
  words it questions our epistemic justification
  for inductive extrapolation.

20
The Inductive Justification

• Max Black (1958) argued that induction can be
  justified inductively without vicious
  circularity, by distinguishing between an
  inductive rule and an inductive premise.
• But Humes question concerns the rational
  well-foundedness of taking the observed as
  evidence for the unobserved. A rule or premise
  can confer this rational grounding only if it is
  itself rationally grounded. So any circularity
  here is indeed vicious.

21
The Pragmatic Justification

• Hans Reichenbach (1949) argued that if there is
  any general rule, deterministic or statistical,
  to be found e.g. that 61 of As are Bs then
  induction will find it, and is better than any
  alternative method.
• But this argument just takes for granted that we
  are looking for an inductively consistent rule
  one that stays the same over time.
• Besides, Humes pragmatic justification is
  stronger we cant help reasoning inductively!

22
Mellor on Warranted Induction

• Mellor takes an externalist approach induction
  is warranted if the world is such as to make
  inductive predictions probably true (e.g. because
  the world does in fact behave consistently over
  time), even if we are unable to know that this is
  the case.
• For the externalist, a belief can be justified by
  how things are, even if the believer is unaware
  of what justifies his or her belief.
• Well consider externalism in Knowledge.

23
Goodmans New Riddle of Induction

• Call something grue if it is first examined
  before noon on 1st April next year and is green,
  or first examined later and is blue. (Bleen is
  the other way round.)
• Suppose all emeralds examined so far are green.
  Then we have two rival theories, both supported
  by all the available evidence
• (a) All emeralds are green. (straight theory)
• (b) All emeralds are grue. (bent theory)
• How can we justify preferring (a) over (b)?

24

• Grue seems artificial because its defined in
  terms of green and blue. But green can be
  defined in terms of grue and bleen!
• The easiest answer is to say that Goodmans bent
  predicates dont latch on to real properties, and
  inductive support depends on real similarities
  between things, not on purely syntactic
  relationships between sentences (unlike formal
  deductive validity).
• To back this up, consider a how miner on 1st
  April could know the colour of an emerald that he
  digs up to tell whether its grue or bleen, hed
  have to know the time.